Drafting instrument



Aug. 5,.1952 E. F. CAMPBELL DRAFTING' INSTRUMENT Filed Dec. 9, 1949INVEN'IOR 35 izzfuaro Cam oell Patented Aug. 5, 1 952 TT;

' Application December 9, 1949, Serial 132.1851

4Clain' s; (01.33-104) 1 i=(Granted-under the act of March amendedApril,30,-1928; 370 O. G. 757) The invention described herein, if Ypatented, may be manufactured and used by or for the Government forgovernmental purposes without the payment to me of any royalty thereon.

This invention relates to drafting instruments and among other objects,aims to provide a device which facilitates the making of. dotted pencillines of different characteristics and which isdesigned to obviatescraping graphite from pencil points, which would smear Or-SOildrawings, Other objects will be obvious from th following description ofthe preferred embodiment of the invention shown. in the accompanyingdrawings forming a part of this specification;

In said drawings:

Fig. 1 is a plan view of the instrument;

Fig. 2 is a fragmentary plan view on a larger scale of one of theremovable line-dotting attachments; I g

Fig. 3 is an enlarged section'on line 3-3 of Fig.1; j i,

Fig. 4. is an enlarged section on line 4-4 of Fig. 2; and l Fig. 5' isan enlarged section on line' 5-5 of Fig. 1. I

Referring particularly to the drawings, the preferred embodiment of theinvention comprises a transparent fiat plastic body 6 which may be a30-60 right triangle as shown or may have many other shapes such as thatof a 45 right triangle, an isosceles triangle, a protractor, a square oroblong, or even a circle. Its edges may be marked with scales in inchesor centimeters and fractions thereof (not shown). This triangle isprovided with three slots each parallel to one of its sides but havingno communication with the others. The purpose of these slots will beexplained presently.

On the underside I, that is, the surface adjacent the drawing paper, thebody 6 is provided with pairs of grooves 8, 9, I0, H, l2, l3, each pairextending parallel to one of the sides of the triangle but spacedtherefrom, and terminating short of the other two sides. These grooveshave depths of about two-thirds or three-fourths of the thickness of thebody and make angles of about 60 or 120 with the plane of the underside1, as shown in Fig. 3, so that the grooves of each pair convergeupwardly.

Interlocked with each converging pair of grooves is a resilientchannel-shaped insert or strip l4, l5, l6, each strip being preferablyof plastic and having converging longitudinal edge flanges l1, l8adapted to enter th grooves when the strip has been bent or flexedtransversely and adapted-when released to lock with the groove walls byreason, of its resilience. Each plastic strip has a thickness of lessthan 1 mm. and any convenient length as indicated by the dimensions ofthe slots in body 6. The purpose of strips l4, l5, I6 is to facilitateforming dotted or dot-and-dash lines and to this end each strip has oneor more series of perforations] 9, '20 (or 22 or 24) of different sizesand spacing. Perforations J9, 20 are primarilyfor making two differenttypes of dotted lines by running apencil (in-the, manner indicated inFig. 4) rapidly-over eitherseries of perforations while guided by the:appropriate edge of slot 25. Perforations 22 in strip 15 are circularand are primarily for making fine dotted lines with the pencil movedalong slot 26, while perforation 24 in strip l6 facilitate making dot-and-' dash lines in'conjunction with slot 21. Slots 26 and 21 arenarrower. than slot 25 and onlyone series of perforations are;associated with these narrow slots. It will be clearthat many otherarrangements and dimensions of the perforations and slots may beemployed, Obviously each strip 14, I5, I6 is easily removed manually forreplace-v ment with a different strip. If desired, after the strips aretaken off, the longitudinal edges of slots 25, 26, 21 may be used fordrawing straight lines, and as the several slots may be of manydifierent widths they may be employed for making parallel lines spaceddifferent known distances apart without the necessity of measuring suchdistances.

While the illustrative strips are snapped on and off the body 6, ifpreferred each pair of grooves 8, 9, or H], H, or l2, 13 may extendtoone edge only of the triangle and th corresponding strip may be engagedtherewith by pushing or sliding it endwise into the groove ends whereexposed at a triangle edge. This will be understood withoutillustration.

As shown in Fig. 4, the edges of the strips which define or bound theperforations Iii-24 are curved downwardly to cause the lead pencil pointto ride over the edges without scraping or abrading any substantialamount of graphite from the point, the result being that no graphitedust is deposited on the drawing paper by ordinary use of theinstrument. It is of course clear that the paper would be smeared orsoiled if such dust were formed.

In the central portion of the triangle or other body 6, several circularseries of perforations 30, 3|, 32, 33 are shown all of which surround ahole 34 whichis at the center of the several circles and is adapted toreceive the point of a compass. After placing the compass point in hole34 the draftsman may make dotted circles of a considerable range ofdiameters by merely running the lead around over the perforations. Thethickness of the body 6 is considerably reduced in the area containingperforations 30, 3|, 32, 33, as indicated at 35, Figs. 1 and 5, so thatthe compass lead mayv enter'every,perforation as it passes around thecircle. Arcuate or curved dottedlines: may be made possible by theprovision of other perforations extending in curved lines (not; shown).These supplementary perforationsmay. be dispensed with and a singlelarge hole f'ortl'ie draftsmans fingers may be provided;asyis-conventional in triangles. Other, changes, may be, made within thescope of the appended claims:

What I claim is:

l. A drafting instrument facilitating the making of broken linescomprising a bod'y having a fiat under surface provided with apair ofparallel grooves extending up into the body, the body also having a:straight slot: extending between saidgrooves; an elongated flexiblestriplha-vi'ng' flanges along two longitudinal edgeswhich extendupwardly-intothe: grooves, theshapes of the grooves and 'flangesbeingcomplementary and suchthat the strip" is-removably locked on the body,the strip havinga very-thin area between itsflangesand having-spacedperforations :in'said thin area, so that a: pencil point -may be thrustthrough-the'slot fromaboveand'may be run along the slot and over theperforations. through: which: the pencil point passes -to mark a; papersheet placed under thebody with dots; or dashe's spaced' inaccordancewith the spacing s che perfora tions 2. Theinv'entionas:defined claim -1; where-- in the b'ody has the shape of a triangleandQther-e are three pairs of grooves; three slots each asso--ciatedwith one pair-iof grooves-,-- and three strips; each slot and"associated' pair of grooves being parallel -to one-'offthe sides of thetriangle, the slots -having-, no commu-nication with each-other, and 1the grooves of each pairconverging u'p wardly- 3. A ruling device fordraftsmen comprising a flat body portion provided with an elongated slotin one face thereof and a relatively narrow elongated groove located oneach side of said slot and parallel therewith, an elongated strip ofmaterial provided with a series of openings or perforations extending;longitudinally of said strip, flanges on the longitudinal edgesof saidstrip disposed in said relatively narrow grooves, the shapes of therelatively narrow grooves and the..fianges being complementary and suchthat thestrip'is 'detachably connected to the flat body portion.

4. A ruling device for draftsmen comprising a fiat'body portion providedwith a slot and a pair of parallel grooves in one face thereof and oneither side of said slot, an elongated strip of thinresilientmaterial'provided with an elongated series of openings orperforations, and a pair of flanges integral with the strip andextending longitudinally thereof and interlocking with said grooveswhen: the; strip is flexedtransverselyto releasably secure said' strip."to saidbody portion, the resilience of. the. strip and the interlockingflangesrand Zgro'oves constituting; the sole means for securing.the-strip, and the-strip being removablemanuallywheneverx it isfiexedtransverse'ly: and its" flanges are movedout of'interlockingengagement: with: said grooves.

EDWARDF. CAMPBELL;-

REFERENCES CITED The followingvrefe'rences are. of record 'in' the fileof this patent:

UNITED STATES PATENTS I I Date Number a Name- 1,662,832 Clark Mail. 20,1928 2,303,676- Bixby D60. 1, 1942 FOREIGN PATENTS Number Country Date.

265,691 Great-Britain Feb. 11,1927

